The changes of acetylcholinesterase in different strains and gender of Culex pipiens pallens

Objective Study the changes of acetylcholinesterase (AChE) activity in different strains of adult male and female Culex pipiens pallens, and provide a basis for the insecticide-resistance detection of mosquitoes by biochemical method. Methods The AChE activity of single mosquito was determined, and acetythiocholine iodide (ATch) as the substrate and 5, 5′-dithio-bis (2-nitrobenzoic acid) (DTNB) as the developer. The insensitivity of AChE to Propoxur was assayed. Results The AChE activity of anti-DDVP (Rd) and anti-Propoxur (Rp) strains of Cx.pipiens pallens was significantly higher than that of susceptible (S) strains, however, the AChE activity of anti-Cypermethrin (Rc) strains was similar to that of S strain. The individual frequency of insensitive AChE of Rd strain and Rp strain was significantly higher than that of S strain, but that of Rc strains was similar to S strain. For S, Rd, Rp and Rc strains, the AChE activity of 3-day-old female mosquito was higher than that of 3-day-old male mosquito. Conclusion The resistance of mosquitoes could be judged by the determination of AChE activity, but a criterion should be different for the male and female mosquitoes.